Hmm... interestingly enough I didn't find this documented. However, I assume that the Windows remote access to command interpreter cmd.exe follows the way how remote terminal sessions work on Unix like systems. On Unix like systems the home directory of user is fully in hands of the operating system administrator. SSH Tectia Server on Unix machine just retrieves home directory as it is defined in the system and it cannot be overridden.

On Windows it seems to be similar, except Windows do not seem have clearly defined concept of a home directory. So SSH Tectia Server on Windows retrieves home directory as whatever is returned from call to GetUserProfileDirectory:

It seems to me then, that if you want to change the folder which will be the CWD after login to SSH Tectia Server, you need to change the profile directory of the user account the user is logging into.

Or you may rather re-consider the solution you are trying to implement.
I am afraid my answer didn't help you much.